Atomic layer annealing with radio-frequency substrate bias for control of grain morphology in gallium nitride thin films

A method of performing atomic layer annealing (ALA) with radio-frequency (RF) substrate bias on insulating and amorphous substrates is demonstrated for GaN deposition at 275 degrees C. GaN is typically deposited by metal-organic chemical vapor deposition ( MOCVD) or molecular beam epitaxy ( MBE) at > 600 degrees C, resulting in strain upon cooling; this makes low-temperature process alternatives desirable. Tris(dimethylamido) gallium (III) and hydrazine served as precursors whereas Ar and Kr were used for ion bombardment. Optimization of substrate bias potential is demonstrated by grazing incidence x-ray diffraction (GI-XRD) and x-ray reflectivity (XRR). Reference films were deposited by thermal ALD and non-substrate-biased ALA processes. X-ray photoelectron spectroscopy (XPS) surface and depth-profiling studies show that applied RF bias decreases film oxygen and carbon content relative to the reference films; these films also show crystallites broadening with increasing film thickness by TEM in contrast to the reference films. In summary, ALA with RF substrate bias is demonstrated as an effective method to deposit GaN thin films at a low deposition temperature on insulators.

Automated summary

This study demonstrates a method of atomic layer annealing (ALA) with radio-frequency (RF) substrate bias for GaN deposition at a low temperature of 275 degrees C on insulating and amorphous substrates. GaN is typically deposited at high temperatures, resulting in strain upon cooling, thus the need for low-temperature alternatives. Tris(dimethylamido) gallium (III) and hydrazine were used as precursors, with Ar and Kr serving as ion bombardment. The optimization of substrate bias potential was evaluated using GI-XRD and XRR. The application of RF bias reduced the oxygen and carbon content in the film and broadened the crystallites. This research highlights the effectiveness of ALA with RF substrate bias for depositing GaN thin films at low temperatures on insulating substrates.